L046 Murray Basin seismic reflection and refraction survey, NSW, VIC, SA, 1960

Between August and December 1960 a seismic party from the Bureau of Mineral Resources carried out a reconnaissance seismic survey, using reflection and refraction techniques, across the Murray Basin. Traverses were placed at selected localities at Carrathool, Hay, Maude, Balranald, Wentworth, Merbein, Lake Victoria, and Loxton. In general, the results show that the Basin, at least along the line of traverse, consists of essentially undisturbed sediments above a high-velocity basement. The thickness of Basin sediments ranges from about 900 ft at Carrathool to 2200 ft at Lake Victoria and Merbein. Most of the sediments are of Tertiary age, with Mesozoic at Loxton and Wentworth and perhaps at other traverses in the western part of the Basin.The seismic velocity in the sediments has a typical value of about 6000 to 7000 ft/sec, while the velocity in the basement ranges from 15,750 ft/sec (at Hay) up to 20,000 ft/sec (at Lake Victoria). The geological nature of basement is not known, but it is considered that it definitely marks the floor of the Tertiary (or Tertiary - Mesozoic) basin. Refraction velocities alone are of doubtful value in identifying the floor, as it is known that crystalline basement, metamorphosed sediments, or unmetamorphosed sediments such as limestone, may have velocities within this range.